Probably not a kit a kit as such , but sears and roebuck did offer some of the first packages that were like a kit with pre manufactured components. First determine the age by looking to see if the beams are hewn (older than 1900) or sawn. Hewn barns were asseble or dry fit then disassembled and stacked until all components where ready. Then a date was set for raising and the call went out and they raise it in a day usually. The marks where reference or "witness" marks to tell what mortice went with which tenon. Barns where usually built on site, (cause thats where the logs were), but if the logs wre elseware they could have been pre-fab off site. As for the cement foundation many old(hewn) barns where elavated (or moved and elavated)to accomadate dairies. If its hewn, with cement base, one of these things probably happened. If sawn, it may be all origanal. I also heard there where companies in the early 1900's making pre fab timber barns, usually engineered structures consisting of smaller 8x8 timbers, short in length and often very large buildings.